1. Field of the Invention
The present invention concerns a procedure for simulating any desired tablet compressing operation, a tablet being pressed of the tablet compound in a trial tablet pressing apparatus.
2. Brief Description of the Background Art
At present, development and set-up for production of a new tablet formulation is most often a cumbersome and time-consuming process. Usually, formulation of the tablet which is being developed is first done with an excenter tabletting machine, then with a small rotation machine, and finally with a big production rotation machine. Therefore, in the worst case, the formulation has to be completely redone several times, owing to the different compressing characteristics of the different machines.
Presently, trial tabletting apparatus are available, referred to as tablet pressing simulators. Devices of this type are experimental presses in which the tablet compound is placed in a pressing matrix, into which from above and from below two punch members are guided to press the compound into a tablet. The motion paths of the punch members during the pressing operation are controlled to be consistent with arbitrarily selected motion paths. Usually, a downward convex step function or a sinusoidal curve is used for a motion path.
The simulation method applied by existing experimental presses is not applicable e.g. in the work serving formulation of the tablet compound because the movements of the punch members of the press are not consistent with the true compression event. It is known that the movements of the punch members, as a function of time, depends among other things on the type, model and production rate of the press which is being used, on the types of punches and matrix, on the characteristics of the material to be compressed, and on the size and shape of the tablet. Sinusoidal punch motions are not even a rough approximation of actual punch motions, and therefore they do not in any way correspond to the true motions of the punches in a press during the precompression, compression and ejection steps. In fact, trial press devices which are called simulators do not at all simulate the compression taking place in tablet presses. Therefore the results derived with their aid are, even at best, durbious as to their significance and interpretation. Owing to the simulating method applied, the practical value of such trial tablet presses is minimal, as is well indicated by the fact that their total number in the whole world is about ten units.